498 engine build N/A carb and intake suggestions?
 

I am removing the whipple and efi from my engine and converting it to a carburetor. I'm not sure what intake and carb will be best for my package.

.070 over 454
4.25 stroke
10.25:1 compression
stock magnum rect port heads with bowl work
CMI sport tube lite headers
Cam is .600/.600 lift 227/235 @.050 on a 112

I would like to make around 550 HP and looking for suggestions on carb/intake selection.

anyone?

Be careful with that much compression, short duration cam and iron heads. I'd start out with 32 degrees of ignition advance and the best pump gas you can find.

Edelbrock Victor and an 850 Holley if you're serious about 550 hp.

I have an Edlebrock Victor Jr., rectangle port, 4150 carb base, port matched with dyno time only; $150 to your door :drink:

Has it been cut or is it out of box?

Intake and Carb
 

Not trying to tell you what to do but we have already built a similar engine. I would use a New style Merlin Intake Single Plane and at least an 850 if not a 950. This intake has extended runners and a raised plenum. It makes more power than a Victor Jr with a Super Sucker Spacer. Another good intake is the New Style Weiand Team G with the Extended Runners and raised Plenum.

Intakes and Carbs
 

By the way, we had the same cubes pretty much and same Compression. But we used a Hyd Roller with about .621 lift and 238 242 Dur @ .050 I think on a 114. Made over 638 HP on Dyno with 34 degrees timing and 93 Octane. It went over 80 MPH in a 22' Donzi. Don't know what kind of heads you are using. That makes a lot of difference too.

well, my heads need a considerable amount of work SOOOO I bought a set of Dart 310 aluminum marine heads unported. I still dont have a cam. I kind of like the Comp XM296HR.

.566/ .566 242/248 @.050 on a 112

Opinions on this?

Mike I have been told the same thing about the Merlin with an 850 Demon for this set up performs about as good as it gets.

Billy... 296 is a tad bumpy... tone the cam down to around what Mike says, 113-114 LS installed LC at 109-110 is a MUST... I know the boat he's talking about... solid runner, good dock manners... Merlin and Demon 850 combo is great if you have hatch clearance room.. I have a 850 Demon on my 22 Donzi and have tuned 3 others just like it, 2 are 540's.. carb is tits.. wheel it to 5400-5450

your pal Al..

What kind of exhaust? (if you have wet headers) Be careful of reversion with too much cam. May want to get around .222 @.050. Depending on the rise and where your water is induced. I'm sure Buiz knows better than me, But I didn't see anyone ask about exhaust.

Mike ^^^

Can anyone provide a link to the Merlin intake you guys are talking about?

Edelbrock 7561? PETO likes the air-gap 2.0 stuff

Thanks guys. I guess I am basically looking for the same performance naturaly aspirated (carb) with a 498" that I had with a whipple and fuel injection. Checkmate 270 Convincor is the hull, it ran a best of 81 mph @ 472" stock magnum heads, mild cam and CMI Sport Tube Lites and 8psi.
Hatch clearance is not an issue, I want to make the thing last and perform. I feel like I am going backwards with a carb and big cam BUT I think it is the best route.

Hey J Im concerned with running too short of a duration with my compression... however I may be ok keeping the blower cam I have with aluminum heads. This boat stuff is alot harder than race cars LOL and I'm dealin with a lot smaller window!

what chamber size on the heads you have now?

I have all new parts. 310 Dart aluminum 121cc chambers
4.070 bore 10.2 compression
4.250 stroke.

I have not bought a cam or intake/carb yet

have you thought about the crane 741 it works good on the 496 combo with good heads and intake , i have done many of these and that cam with a good single plane intake and at least a 950 and you are at 600+ hp . we did a pair using that cam and the edelbrock victor intake with a 1050 and made 640 hp at 5600rpm , they are in a 32 active thunder that runs 92 on the gps so we know the power is there.

that works out to a 448 not a 498...

.070 over 454 4.320 4.250 stroke I'm crunchin so many numbers I confusin myself!

Sorry for the late response, I have been ill.
the manifold is port matched, can be seen in the photos here
http://www.offshoreonly.com/forums/s...-rec-port.html

I went with a custom grind from Comp (my cam supplier). It is a .615/.651 lift 236/244 @.050 dur on a 112 lobe sep.